1. Field of the Invention
The present invention relates to a method and system for preventing the spillage of liquid fuel to the ground adjacent the system sump or manhole.
2. Description of Related Art
Gasoline dispensing stations generally include a large underground holding tank, also called a storage tank, and a pump to transfer gasoline from the holding tank to a vehicle gasoline tank. There are a variety of configurations, but in addition to the holding tank and pump, most include a sump having a cover which is at or near the ground surface. The transfer pump may be a pump/motor combination located in the holding tank or in the sump. Alternately the transfer pump may include the pump in the storage tank and the motor in the sump and driving the pump in the holding tank. In operation the pump forces the gasoline up through a conduit to a location above the level of the ground.
Distinction is made between a pump and a pump/motor combination. A pump is referred to as a device which provides fluid flow and uses an external device for providing the motion to power the pump. The external device may be a motor which provides rotation to the internals of the pump such as in a centrifugal pump, turbine pump or positive displacement pump. A pump/motor combination includes both the pump and motor in the same casing as in a submersible well pump, the motor having a seal for preventing liquid from entering the motor. The term “transfer pump” refers to a pump, whether the motor is directly attached to the pump in the same casing or the motor is located a distance from the pump.
A sump may contain a motor, pump, fill line, gasoline transfer line or venting equipment. A riser assembly extends between the holding tank and the sump and may enclose transfer conduits, a drive shaft, control equipment or any other dispensing equipment. The sump, located below ground level, may be prone to having surface water enter through open portions, unsealed portions and through portions which include an aged seal no longer able to keep the surface water from entering. Surface water can include rain water, overflowing stream, river or bay water, overflowing sewage or storm drain water, liquid soap solution, vehicle coolant, or any other liquid that a vehicle or person can spill. When gasoline is already in the sump from leaks or over filling, the surface water mixes with the gasoline. When the level of fluid is beyond that which the sump can hold, the result is overflowing of the fluid to the adjacent ground, thereby threatening contamination of the adjacent ground or ground water. The gasoline in the overflow causes a hazardous situation in which regulatory agencies must be alerted, generating hefty cleanup fees and fines.
The pressure needed to force the gasoline upward often causes leaks in the distribution equipment including the transfer pump, conduit, sump, dispensing apparatus or any of the connections within these components. The sump generally includes an alarm system to warn an attendant of gasoline or surface water leaking into the sump and causing an overflow condition. However, the delivery systems are so automated and so complicated that the average employee often does not completely understand the different alarm signals. As a result, the employee may view them as a nuisance and all too frequently just turns the alarm off. Whether it is from ignorance or false belief that there is an automated removal system for the gasoline, surface water or any other fluids in the sump, the alarm is often turned off when sounded and nothing is done immediately (or ever) to remedy the mixture of gasoline, surface water or fluids in the sump. Accordingly, there is a need for an automatic sump overflow prevention system and method that affords additional time for fuel station owners and operators to keep problems contained and avoid ground and groundwater contamination and expensive attendant clean-up costs.